Photovoltaic (PV) arrays, e.g., roof top mounted solar panels, are becoming more widely used as the manufacturing costs are reduced. In a large system a plurality of solar panels are connected in series to increase the power output by the system.
For example, some large PV systems may include 15 to 33 solar panels connected in series. The output voltage associated with an individual PV array may be in the range of 38 to 48 VDC, which results in the operating voltages of 600 to 1500 volts for large PV systems. Such high voltages are output by the PV system when illuminated.
Current systems provide no method of controlling or shutting down the output voltage of a PV system. The inability to controllably power down a PV system presents a problem for emergency personnel when an emergency arises in a building with PV systems providing power in the building. In traditional power systems a main power disconnect may be used to remove power from the building power system, to insure the safety of emergency personnel during their operations in the building. The danger to personnel in an emergency is further increased because the voltage of the large PV system may exceed the line voltage of traditional power systems.
The higher voltage of the PV system is normally distributed over much of the roof area of a building where the solar panels are interconnected. In the event of fire for instance, water may be sprayed on the roof of the building, creating an electrical shock hazard if the panels and wire conductors are exposed to water. To overcome these hazardous situations, many governmental authorities are enacting regulations requiring some means of panel shutdown.
There is a need for providing a means of safely disconnecting power from a PV system to prevent hazardous electrical conditions.